How quickly do OCI rejections come in?

I've had a number of OCI screening interviews and have a callback from one. Two of the firms have started making their call-back phone calls - but unfortunately not to me. Oh well, that's the way it goes. How long would you expect to wait before receiving the rejection email/letter? I would have thought that it would have been pretty quick, but it's been almost a week and I've heard nothing. (The friend who got the callbacks was actually rejected by the firm that gave me the callback, and she found out the same day as me.) I am not harboring any hopes that I will get a callback, but just interested in other people's experiences. Thanks.